I have regularly been particularly conscientious about replacing the air filters in the gas furnace & air conditioner every week, but i schedule professional maintenance for the furnace in the fall & the cooling plan in the Spring. I am not sure why I forgot about taking care of the air duct. I recognize that because the pipes are hidden in the walls & ceiling, I just never considered the need for service. I was not cheerful when my gas furnace had trouble keeping the cabin warm last winter; The heating plan seemed to be running non stop & yet the temperature was inconsistent from 1 room to another, then no matter how high I adjusted the thermostat, the cabin felt cold. The gas furnace is not that outdated & should have been able to handle the cold weather. I also observed that there seemed to be a lot of dust floating around, & my weekly energy bills were higher than normal. I finally hired an Heating, Ventilation & A/C business to check out my gas furnace. The specialist checked the heating plan & found that the problem was caused by the air duct. There was a considerable buildup of contaminants in the pipes. The accumulation of dust, pet dander, pollen, mold growth & even dead rodents was blocking airflow through the pipes. Because the maximum amount of air was failing to reach the several rooms, it was forcing the gas furnace to run more often, toil harder & use more energy. There was greater wear & tear on the gas furnace. The specialist provided a duct cleaning service using device that looked a lot love an industrial vacuum cleaner.